This program will focus on the isolation of a component of the Paracoccus denitrificans iron transport apparatus. The major aim of the program is to selectively and irreversibly label the microorganism's siderophore surface receptor in order to facilitate its isolation and eventual structural elucidation. The hope is that the isolation of this receptor will provide us with a better understanding of how the organism utilizes its siderophore, parabactin, in the assimilation of iron. The program will be divided into two segments: 1) the design and synthesis of a parabactin receptor label and 2) the fixing of the parabactin label to the Paracoccus denitrificans parabactin receptor. The preliminary evidence presented in the text to follow strongly suggests that the program has a high index of success. We have already demonstrated our expertise in synthesis of related systems as well as our ability to handle the associated microbiological manipulations.